Circuit interrupter



Dec. 17, 1946. B BAKER ETAL 2,412,858

CIRCUIT INTERRUPTER Filed Feb. 10, 1943 3 Sheets-Sheet 1 WTTNESSES: INVENTORS Z BL WOm/n Packer and g 7 h/l'nfhrop A4 Lee 06,

Dec. 17, 1946. B. P. BAKER ET AL 0 IRCUI T INTERRUPTER Filed Feb. 10, 1943 3 Sheets-Sheet 3 Patented Dec. 17, 1946 UNITED STATES CHRCUIT INTERRUPTER Benjamin P. Baker, Turtle Creek, and Winthrop M. Leeds, Wilkinsburg, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application February 10, 1943, Serial No. 475,394

6 Claims.

to obtain adequate pressure for low current interruption, it is desirable to make the contact separation for the pressure generating are sufiicient to provide adequate pressure to interrupt low currents.

Also there is a need for a considerable gap in clear oil for the pressure generating contacts to obtain high dielectric strength during a closing operation as applied to the type of circuit interrupter in which the interrupting arc is established after the establishment of the pressure generatin arc.

We have found that if the interrupter is designed to take care of low current interrupting conditions, that is, having a relatively large contact separation for the pressure generating contacts to obtain adequate pressure and also to obtain a considerable gap in clear oil during a closing operation, that occasionally during high current interruption excessive pressures are produced in the chamber housing the pressure gencrating contacts.

It is, therefore, desirable to provide means for limiting the excessive pressure obtained during the interruption of circuits of high power. Preferably such means should shorten the pressure generating gap automatically in response to the pressure created at the pressure generating gap.

It is an object of our invention to provide an improved circuit interrupter having a pair of contacts, at least one or which is movable to establish an arc and to lengthen the same, and to provide means responsive to the pressure created by the are to halt the movement of the movable contact, and hence to prevent a further lengthening of the are which would have resulted if the contact had continued its movement.

A-further object of our invention is to provide an improved circuit interrupter of the type in which both a pressure generating arc and an interrupting are are established, and to provide means responsive to the pressure created at the pressure generating arc to shorten the pressure generating arc.

Another object is to provide an improved circuit interrupter of the type in which a pressure generating arc is established and utilized for forcing fluid under pressure toward an interrupting arc to facilitate the latters extinction, and to provide piston means responsive to the pressure created by the pressure generating arc to shorten the pressure generating arc, the piston means also being operative to facilitate the interruption of low current arcs.

Another object is to provide a circuit interrupter of the type described in the immediately preceding paragraph in which the piston means has relief openings which are uncovered during excessive pressure to relieve the excessive pressure.

Another object is to provide an improved circuit interrupter having a normally stationary contact and a cooperable movable contact which is movable away from the stationary contact to draw an arc and to lengthen the same, and to provide means responsive to the pressure created by the arc to move the stationary contact toward the movable contact to shorten the arc.

Further objects and advantages will readily become apparent upon a reading of the following specification taken in conjunction with the drawings, in which:

Figure lis an elevational view, partly in section, of a circuit interrupter embodying our invention;

Fig. 2 is an enlarged elevational view, in vertical section, of one of the arc extinguishing units shown in Fig. 1, the unit being shown in the closed circuit position;

Fig. 3 is a view similar to Fig. 2 but showing the disposition of the parts during the interruption of low current arcs;

Fig. 4 is a vertical sectional view taken along the line IV-IV of Fig. 2;

Fig. 5 is a view in section taken along the line VV of Fig. 2;

Fig. 6 is an enlarged fragmentary view taken along the line VIVI of Fig. 3;

Fig. 7 is a fragmentary elevational view in section of the arc extinguishing unit shown in Figs. 2 and 3 but showing more clearly the shortened length of the pressure generatin arc and the position of the piston means during the interruption of very high current arcs;

Fig. 8 is an enlarged elevational View, partly in section, of a modified type of arc extinguishing unit incorporating our invention and shown in the closed circuit position; and

Fig. 9 is a view similar to Fig. 8 but showing the disposition oi the parts during the interruption of high current arcs.

Referring to the drawings, and more particularly, to Fig. 1, the reference numeral I designates a tank filled to the level indicated with a suitable arc extinguishing fluid 2, in this instance oil. Suspended from the cover 3 of the tank I are insulating bushings 4, 5 surrounding terminal studs, not shown. At the lower end of the insulating bushings i, 5 are threadedly attached and clamped to the terminal studs contact feet 6, l.

The contact feet 6, 1 support are extinguishing units or chambers, generally designated by the reference numeral 8. In the closed circuit position of the interrupter, as shown by the full lines in Fig. 1, the two are extinguishing units 8 are electrically connected by a conducting cross bar 9. The cross bar 9 is reciprocably operated in a vertical direction by an insulating operating rod lit, which is actuated by suitable operating mechanism, not shown. At the opposed outer ends of the conducting cross bar 9 are disposed movable contacts ll, [2.

Referring more particularly to Fig. 2, it will be observed that an upper pressure generating contact I3 is pivotally mounted at l4 within the arc extinguishing unit 8. A top dome casting l5 encloses the upper pressure generating contact l3, as shown in Fig. 2. An inspection plate I! may be provided so that one may view the interior of the top dome casting I 5 without disassembling the arc extinguishing unit 8.

The dome casting provides an enclosed pressure generating chamber, generally designated by the reference numeral l8. Cooperable with the pressure generating contact 13 is an intermediate contact l9 having a flange portion 29 which serves as a lower seat for a compression spring 2! The compression spring 2| biases the intermediate contact I 9 in a downward direction.

When the pressure generating contact l3 moves upwardly, as shown in Fig. 3, to separate from the intermediate contact ill, a pressure generating are 22 is established. The movable contact ll also cooperates with the intermediate contact I 9 to establish an interrupting are designated by the reference numeral 25 in Figs. 3 and 7.

The are extinguishing unit or chamber 8 is formed by assembling a plurality of suitably shaped insulating plates upon insulating tie rods 21.

The are passage portion of the arc extinguishing unit 8 is described and broadly claimed in a patent application of Leon R. Ludwig, Be P. Baker, and Winthrop M. Leeds, filed November 11, 1942, Serial No. 465,244, entitled Circuit interrupters, and assigned to the assignee of this application. The aforesaid application completely describes each of the. insulating plates utilized in forming arc passage portion of the are extinguishing units 3, and, therefore, merely a brief description thereof is necessary. This application also claims the mechanism partly hereinafter disclosed of maintaining the proper contact pressure between the contacts and also the mounting for the pressure generating contact l3.

It will suifice to state that vertical flow passages, generally designated by the reference numeral 2 5, are provided by the arc extinguishing units 6 to connect the pressure generating chamher It with a plurality of lateral inlet passages 25 for conducting fluid, in this instance oil, under pressure toward the interrupting are 23, The fluid, after contacting the interrupting are 23,

passes out of the are extinguishing unit 8 through lateral exhaust passages 26, more clearly shown in Fig. 4. The pivotally mounted pressure generating contact l3 has rigidly secured thereto two actuating arms 28 which are disposed externally of the arc extinguishing unit 8. A pin 29 passes through the two actuating arm 28 and pivotally "2 the compression spring 35.

4 supports a link member 30, as shown more clearly in Figs. 2, 3 and 6.

Referring more particularly to Fig. 6, it will be observed that a pin 3| passes through the lower end of the link member 30, and also the pin 3| passes through two slots 32 disposed in the upper bifurcated portion 33 of an insulating operating rod 36. A washer member 34, having a rectangular aperture formed therein to permit a sliding of the washer member 34 on the bifurcated portion 33 of the operating rod 36, is disposed below the pin 3| and serves as an upper seat for a compression spring 35. The lower end of the compression spring 35 seats upon a flange portion 31 of the insulating operating rod 36.

Slidable on a restricted portion 46 of the operating rod 36 is a piston 38 having disposed therein a plurality of relief ports 39 more clearly shown in Figs. 5 and 6. The restricted portion Ml suddenly widens at 4| to form a shoulder.

The operating rod 36 is guided by an aperture 452 disposed in one of the insulating plates 43. The insulating plate 43 serves as an upper seat for an accelerating compression spring 44, the lower end of which rests upon a washer 45 rigidly secured to the operating rod 36.

A flexible conductor 46 electrically connects the dome casting l5 with one of the arms 28 and hence with the pressure generating contact l3.

In the closed circuit position of the interrupter, as shown in Fig. l, the electrical circuit therethrough comprises the left-hand terminal stud, not shown, the contact foot 6, the dome casting l5 (see Fig. 2), flexible conductor 45, pressure generating contact l3, intermediate contact 59, movable contact I I through the right-hand arc extinguishing unit 8 to the contact foot l, and finally to the right-hand terminal stud, not shown.

It will be observed that in the closed circuit position of the interrupter, as shown more clearly in Fig. 2, the pin 3| is positioned partway down in the slots 32 provided in the bifurcated portion 33 to cause the washer member 34 to compress This provides the requisite contact pressure between the pressure generating contact !3 and the intermediate contact 19. Consequently, we have provided a resilient lost motion connection between the operating rod 36 and the link member 38 which operates the actuating arms 28. The structure to effect this resilient lost motion connection is more clearly shown in Fig. 6.

When it is desired to break the electrical circuit passing through the interrupter, or when overload conditions exist in the electrical circuit controlled by the interrupter, suitable operating means, not shown, move the insulating operating rod l0 downwardly to move the conducting cross bar 9 and the movable contacts H, it also downwardly. This downward movement of the cross bar 9 permits the accelerating compression spring 44 to move the operating rod 36 downwardly.

Referring more particularly to Fig. 3, it will be observed that downward movement of the cross bar 9 cause substantially a simultaneous separation of the contacts I I, ill from the intermediate contact I9 to draw substantially simultaneously an interrupting are 23 and a pressuregenerating are 22. The gas escape valve 16 closes as a result of the pressure produced at the pressure generat-' in are 22 within the pressure generating chamber E8. The pressure thus produced within the pressure generating chamber 18 forces fluid, in this instance oil, under pressure downwardly through the vertical flow passages 24 and through the inlet passages 25 toward the interrupting are 23, as more clearly shown by the arrows in Fig. 3. After contactingthe interrupting are 23, the contaminated fluid, in this instance oil, passes out of the arc extinguishing unit 8 through the exhaust passages 26, as indicated by the arrows in Fig. 4.

If now the pressure produced by the pressure generating are 22 within the pressure generating chamber [8 is high enough when acting upwardly against the piston 38 to overcome the downward biasing force as exerted by the accelerating compression spring M, the downward movement of the operating rod 35 will be halted. This will prevent the pressure generating contact itfrom continuing the lengthening of the pressure generating are 22, which lengthening would further increase the pressure within the pressure generating chamber I8.

If the pressure produced by the pressure generating are 22 is sufiiciently high, the piston 38 will be moved upwardly to cause the operating rod 36 to reverse its motion and to result in a shortening of the pressure generating are 22, as more clearly shown in Fig. '7. If the pressure produced by the pressure generating are 22 becomes excessive, the piston 38 will move upwardly to the stop 48, holding the pressure generating are 22 to a fixed predetermined minimum length, and the pressure will act through the relief ports 39 to raise the flange portion 3! to permit a venting of the fluid throu h the relief ports 39 and out of the unit 8, as. shown by the arrows in Fig. 7. The foregoing high pressure conditions exist during the interruption of high current arcs.

During the interruption of low current arcs the pressure created by the pressure-generating are 22 will correspondingly be low. In thi case, the accelerating compression spring 44 will force the insulating operatin rod 36 to follow the downward movement of the cross bar 9. The flange portion 31 of the operating rod 36 will move downwardly to close the relief ports pick up the piston 33 to move the piston downwardly in the piston chamber, generally designated by the reference numeral it, to produce a supplementary oil flow by piston action during low current interruption.

It is thus apparent that during high current interruption, our interrupter operates to halt the further lengthening of the pressure generating arc, and even to reverse the movement of the pressure generating contact l3 to shorten the pressure generating are 22.

It will furthermore be observed that durin the closing operation the flange portion 3? is first moved upwardly to open the relief ports 38 to permit rapid entrance of oil into the piston chamber 41 through the relief ports This speeds the closing operation, and insures that a fresh supply of uncontaminated fiuid is provided in the piston chamber 1'! for the next opening operation of the interrupter. During the closing operation, the insulating operating rod 35 moves upwardly to cause the pressure generating contact it to downwardly to contact the intermediate contact is at substantially the same time that the movable .contact I l engages the intermediate contact it). Thus, it will be observed that we provide a practically simultaneous opening and closing of the contact gaps.

In the modified type of arc extinguishin unit or chamber 59, asshown in Figs. 3 and we provide a modified top dome casting 5i to which an off-standing piston chamber casting 52 is rigidly chamber casting 52. A co. pression 56 moves the head ll downwardly as she in Fig. 8

until the adjusting nut 12? strikes the casting 52.

Apertures Eel are provided at the upper end of the piston chamber casting 52 to relieve any back pressure on the relief valve piston 55.

The relief valve piston 55 is pivotally secured to a link member 58, the lower end of which is pivotally secured to the right-hand end 59 of the pressure generating contact I3.

Bolts not shown secure a flexible shunt 51 both to the dome casting 5i and also to the pressure generating contact l3. A compression spring 62 is disposed between the pressure generating contact I3 and the dome casting 5! and is maintained in position by the heads of the bolts securing the shunt ti.

In the modified type are extinguishing unit 50, arrangement is made for a sequential break, that is, the pressure generating are 65 is formed before the establishment of the interrupting arc 6?. The intermediate contact 53 has a flange portion be which serves as a lower seat for a compression spring 65. The compression spring 65 biases the intermediate contact 83 in a downwardly direction.

In the closed circuit position of the interrupter, as shown in Fig. 8, the movable contact H has forced the intermediate contact 63 upwardly against the biasing action exerted by the compression spring 65 to engage the pivotally mounted pressure generating contact l3. The compression spring 6'2 provides the requisite con tact pressure between the pressure gen rating contact 13 and the intermediate contact 53. The electrical circuit through the modified type are extinguishing unit 59 comprises the contact foot modified top dome casting 5i, shunt 2i, pressure generating contact l3, intermediate contact lower contact ll, cross bar 9 to the other arc extinguishing unit not shown.

During the opening operation, the conducting cross bar 9 is moved downwardly by suitable mechanism, not shown. The intermediate contact 63, being biased downwardly by the compression spring remains in engagement with the movable contact H.

The pressure generating contact l3, under the biasing action exerted by compression spring E2, rotates in a counter clockwise direction about the pivot it, thus following the initial downward movement of intermediate contact 63. This r0- tative movement continues until the piston strikes and is stopped by the stud l2, compression spring being much stronger than compression spring 62.

When pressure generating contact i stops its countencloclnvise rotation about vot inter" mediate contact ES separates therefrom to draw a pressure generating are 86.

Subsequently, the movable contact 5 i separates from the intermediate contact 3 to draw an int upting are 5? (see Fig. 9). The fluid flow from the pressure generating are $3 toward the interr pting arc is? is as indicated by the arrows in 9. The vertical flow passages 24;, the inlet passages 25, and the exhaust passages 25 are identical to those previously described in connection with the interrupter shown in Figs. 2, 3, and

7 4. ConsequentlyQa further description thereof seems unnecessary.

During the interruption of high current arcs, the pressure generated at the pressure generating are 66 may be sufficient to overcome the compression spring 56 and force the relief valve piston 55 and stud l6 upwardly to result in a cunterclockwise rotation of the pressure generating contact L to shorten the pressure generating arc 65.

During the existence of excessive pressure conditions within the pressure generating chamber is, as caused by very high current arcs, the piston 55 and stud it may be moved upwardly a suflicient distance to uncover the relief openings 5% to permit fluid under pressure to escape out of the unit Ml through the relief openings 54.

Consequently, in this embodiment of our invention, we provide a pivotally mounted normally stationary pressure generating contact 13 which under excessive pressure conditions is rotated to shorten the pressure generating arc 55. Under excessive pressure conditions, not only is the pressure generating arc 66 shortened, but also relief openings 5 are uncovered to permit a venting of excessive pressure out of the unit 56.

During the normal operation of the interrupter, that during the interruption of low current arcs, the pressure generating contact it remains in a relatively stationary position, the compression spring 62 not serving to shorten the pressure generating are 66. The compression spring 62 merely produces the requisite contact pressure between contacts i3, 63, and has no function during high or low pressure conditions.

Although we have shown and described specific structures, it is to be clearly understood that the same are merely for purposes of illustration, and that changes and modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

We claim as our invention:

1. In a circuit interrupter, a pivotally mounted pressure generating contact, an intermediate contact cooperable with the pressure generating contact to draw a pressure generating arc, a movable contact cooperable with the intermediate contact to draw an interrupting are, an operating rod movable in response to motion of the movable contact to actuate the pressure generating contact, and piston means operatively connected to the operating rod and responsive to the pressure of the pressure generating arc to halt the opening movement of the pressure generating contact during high pressure conditions. 2. In a circuit interrupte a pivotally mounted pressure generating contact, an intermediate contact cooperable with the pressure genera-ting contact to draw a pressure generating arc, a movable contact cooperable with the intermediate contact to draw an interrupting arc, an operating rod movable in response to motion of the movable contact to actuate the pivotally mounted pressure generating contact, and piston means operatively connected to the operating rod and responsive to the pressure of the pressure generating arc to reverse the opening movement of the pressure generating contact to shorten the pressure generating arc during high pressure conditions.

3. In a circuit interrupter, a pivotally mounted pressure generating contact, an intermediate contact cooperable with the pressure generating contact to draw a pressure generating are, a movable contact cooperable with the intermediate contact to draw an interrupting arc, an operating rod movable in response to motion of the movable contact to actuate the pivotally mounted pressure generating contact, and piston means operatively connected to the operating rod and responsive to the pressure of the pressure generating arc to halt the opening movement of the pressure generating contact during high pressure conditions, the piston means having relief ports which are uncovered during excessive pressure conditions to relieve the pressure.

4. In a circuit interrupter, a pivotally mounted pressure generating contact, an intermediate contact cooperable with the pressure generating contact to draw a pressure generating are, a movable contact cooperable with the intermediate contact to draw an interrupting arc, an operating rod movable in response to motion of the movable contact to actuate the pressure generating'contact, and piston means operatively connected to the operating rod and responsive to the pressure of the pressure generating arc to reverse the opening movement of the pressure generating contact to shorten the pressure generating arc during high pressure conditions, the piston means having relief ports which are uncovered during excessive pressure conditions to relieve the pressure.

5. In a circuit interrupter of the fluid immersed type, means for establishing and lengthening a pressure generating arc, means for establishing an interrupting arc, fluid flow passage means leading from said pressure generating are to said interrupting arc whereby said pressure generating arc forces fluid under pressure into engagement with said interrupting arc to assist in extinguishing said interrupting arc, fluid moving means in communication with said passage means, means for actuating said fluid moving means during low current interruption to force fluid through said passage means toward said interrupting arc in addition to that moved by said pressure generating arc, and means whereby said fluid moving means is actuated by the pressure created by the pressure generating are under high current interruption torender said first-named means ineifective to continue lengthening the pressure generating arc.

6. In a circuit interrupter of the fluid immersed type, means for establishing and lengthening a pressure generating arc, means for establishing an interrupting arc, fluid flow passage means leading from said pressure generating arc to said interrupting are whereby said pressure generating arc forces fluid under pressure into engagement with said interrupting arc to assist in extinguishing said interrupting arc, fluid moving means in communication with said passage means including a piston chamber and a piston operative within said chamber, means for actuating said fluid moving means including spring means for actuating said piston during low current interruption to force fluid through said passage means toward said interrupting arc in addition to that moved by said pressure generating arc, and means whereby said fluid moving means is actuated by the pressure created by the pres-v sure generating-arc under high current interruption to render said first-named means ineffective to continue lengthening the pressure generating arc.

BENJAMIN P. BAKER. WINTHROP M. LEEDS. 

